Hydrogen has received attention as a main energy source which may replace conventional energy sources in the future since it is light, abundant, and efficient in environments. However, since impurities are included in hydrogen obtained from resources including hydrogen, such as water, natural gas, coal, biomass, and the like, hydrogen should be separated and purified in a process before its use.
As methods of separating and purifying hydrogen, a large number of techniques such as a cryogenic air separation method, an adsorption method, or a hydrogen separation method using a separation membrane have been proposed. Among theses, the hydrogen separation method using the separation membrane is one of widely used hydrogen separation methods since it has advantages in that it may save energy more effectively and may be more easily handled than the other hydrogen separation methods, and instruments may be manufactured in a smaller scale.
In particular, since a palladium-based metal separation membrane has high hydrogen permeability and excellent hydrogen separability, the hydrogen separation method using the separation membrane is clearly superior to the other separation methods. Also, the hydrogen separation method using the palladium-based metal separation membrane may be used in fuel cells, or used to efficiently obtain pure hydrogen for other processes in which hydrogen is consumed, and may be applied in various fields such as use in a hydrogenation or dehydrogenation process so as to increase the number of target products.
Such a metal separation membrane is generally used in such a way that it is stacked on a surface of a porous support, and used so as to improve a hydrogen permeation rate. However, when a metal separation membrane is directly formed on a surface of the porous support made of a metal material in the porous support, the hydrogen permeability may be reduced due to interdiffusion therebetween. Therefore, a buffer layer made of a ceramic material should be sandwiched between the porous support and the metal separation membrane. A sol-gel method has been used as a method of forming such a buffer layer.
However, although the buffer layer formed using a conventional sol-gel method may restrain the diffusion between the porous support and the metal separation membrane, a bonding force between the porous support and the metal separation membrane may be reduced due to the presence of the buffer layer sandwiched therebetween. For example, as shown in FIG. 10, a metal separation membrane 130 may be peeled off from a porous support 110.